A thief wants to board a ship that is anchored at sea by climbing up a ladder that hangs at its side. He rows his small boat to the ship but to his dismay the bottom of the ladder is 2 feet above his reach. He cannot jump up because the small boat will capsize. Not to give up, he figures that the tide is rising by 1 foot per hour and as the tide rises so is his boat and soon he would be able to grab the ladder.

How long would the thief have to wait at sea before the ladder is within his reach?